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From "Mark Grover (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-9000) LAST_VALUE Window function returns wrong results
Date Mon, 01 Dec 2014 16:12:13 GMT
Mark Grover created HIVE-9000:
---------------------------------

             Summary: LAST_VALUE Window function returns wrong results
                 Key: HIVE-9000
                 URL: https://issues.apache.org/jira/browse/HIVE-9000
             Project: Hive
          Issue Type: Bug
          Components: PTF-Windowing
    Affects Versions: 0.13.1
            Reporter: Mark Grover
            Priority: Critical
             Fix For: 0.14.1


LAST_VALUE Windowing function has been returning bad results, as far as I can tell from day
1.

And, it seems like the tests are also asserting that LAST_VALUE gives the wrong result.

Here's the test output:
https://github.com/apache/hive/blob/branch-0.14/ql/src/test/results/clientpositive/windowing_navfn.q.out#L587

The query is:
{code}
select t, s, i, last_value(i) over (partition by t order by s) 
{code}

The result is:
{code}
t              s                    i          last_value(i)
-------------------------------------------------------
10	oscar allen	65662	65662
10	oscar carson	65549	65549
{code}

LAST_VALUE(i) should have returned 65549 in both records, instead it simply ends up returning
i.

Another way you can make sure LAST_VALUE is bad is to verify it's result against LEAD(i,1)
over (partition by t order by s). LAST_VALUE being last value should always be more (in terms
of the specified 'order by s') than the lead by 1. While this doesn't directly apply to the
above query, if the result set had more rows, you would clearly see records where lead is
higher than last_value which is semantically incorrect.



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